PARIS—
Renault SA
RNO 0.29%
appointed interim leaders to manage the French auto maker and oversee its share of a globe-spanning alliance with
Nissan Motor Co.
NSANY 0.86%
after the arrest of Chief Executive Carlos Ghosn in Japan.

After a meeting late Tuesday, Renault’s board said it had appointed Thierry Bolloré, the company’s No. 2 executive, to serve as deputy CEO on a temporary basis. Philippe Lagayette, Renault’s lead independent director, was named as interim chairman, the company said.

Renault is moving to fill a power vacuum that Mr. Ghosn’s arrest created atop the French company and its alliance with Nissan. Japanese prosecutors detained Mr. Ghosn, an auto-industry titan and one of the world’s best-known business executives, after Nissan went to Japanese authorities with details of an internal probe that alleged he incorrectly reported his compensation in filings over many years. The Japanese auto maker said it would seek to oust Mr. Ghosn from his position.

Describing Mr. Ghosn as “temporarily incapacitated,” Renault’s board said the 64-year-old executive would formally retain his posts as chairman and CEO of the car maker. However, the board said it was delegating all of his powers to Messrs. Bolloré and Lagayette.

By deputizing Mr. Bolloré, Renault’s board empowered him to wield Mr. Ghosn’s voting rights on the board of Renault-Nissan BV, the Dutch joint venture that manages the auto makers’ alliance, according to people familiar with the matter.

That move is crucial, the people said, because it preserves the balance of power that Renault and Nissan share in the joint venture. Renault-Nissan BV is jointly funded by Renault and Nissan, with Mr. Ghosn as its CEO and a board made up of executives from both companies, according to Dutch corporate filings.

The Dutch firm has become a focal point of Nissan’s scrutiny. Nissan informed Renault on Monday that it has evidence of potential wrongdoing at Renault-Nissan BV, according to the people familiar with the matter.

On Tuesday, Renault’s board said it was requesting that Nissan “provide all information in their possession arising from the internal investigations related to Mr. Ghosn.”

Renault-Nissan BV manages long-term strategy for the partnership and owns subsidiaries responsible for tasks including joint purchasing and information-technology services. Its expenses, which totaled more than €150 million ($170 million) in 2016, include management fees for executives, services provided to alliance partners and payments to outside consultants, according to the Dutch filings.

The appointment of Messrs. Bolloré and Lagayette came after a request of the French government, which is concerned Mr. Ghosn’s arrest risks weakening the alliance.

“I spoke today on the phone with the Japanese economy minister and we will do everything we can to entrench the alliance,” Economy and Finance Minister Bruno Le Maire told Parliament on Tuesday.

Nissan’s growth in recent years has made it the larger of the two companies, selling more cars than its French partner and contributing heavily to Renault’s profit. That has given rise to fears among French unions and government officials that a creeping “Nissanization” is under way.

As Renault and Nissan have moved toward a unified production system—allowing models from either company to be built at any alliance factory in the world—workers in France have worried that jobs could be easily moved out of the country, where labor costs have historically tended to run high.

The alliance, which in 2016 added
Mitsubishi Motors Corp.as a partner, says it generates savings through joint purchasing of parts and equipment, as well as common engineering of the basics of vehicle design. Its shared functions include human resources.

The alliance said that in 2017 it generated €5.7 billion in savings for its members, up from €5 billion a year earlier.

Auto executive Carlos Ghosn was the architect of an alliance between Nissan, Renault and Mitsubishi, a rare success story of auto makers working together. WSJ reporters analyze the impact on his legacy after his arrest over financial misconduct. Photo: Getty Images